Improvement of Thin Palladium and Platinum Silicide Films on (100) Si Substrates by Incorporating Phosphorus Dopant
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Improvement of Thin Palladium and Platinum Silicide Films On (100) Si Substrates By Incorporating Phosphorus Dopant M. H. Juang1, C. I. Ou-Yang1, H. C. Cheng, and C. T. Lin Department of Electronics Engineering, National Chiao-Tung University, 300 Hsin-Chu, Taiwan, Republic of China 1 Department of Electronics Engineering, National Taiwan University of Science & Technology, Kee-Lung Rd., 106 Taipei, Taiwan ABSTRACT Effects of phosphorus dopant on thin Pd and Pt silicide films on (100) Si substrates have been studied. As for the samples formed by implanting BF2 dopant into thin Pd films deposited on Si substrates and then annealing, the thermal stability of thin Pd2Si films can be improved relative to the control samples without dopant incorporation. The degree of improvement is affected by the fluorine concentration around the silicide/Si interface and thus the BF2 implant energy. On the other hand, as for the samples formed by implanting phosphorus dopant into thin Pd films and then annealing, both the thermal stability and the silicide conductivity of thin Pd2Si films can be significantly enhanced. The large improvements in the thermal stability and the silicide conductivity are nearly independent of the phosphorus implant energy, and which are primarily due to the formation of textured Pd2Si structures. In addition, the Pt silicides formed by implanting phosphorus dopant into thin Pt films and then annealing also show considerably improved thermal stability. INTRODUCTION The salicide (self-aligned-silicide) technology has become an essential part of the fabrication process for recent ultra-high-speed CMOS logic LSI circuits [1]. Metal silicides can be used to reduce the parasitic resistance in LSI circuits, thus enhancing the performance of deep submicron CMOS devices. Previously, several schemes should be employed to form a silicided shallow junction. A method to make silicided shallow junctions is to implant dopant through a deposited metal layer and then subsequent drive-in and silicidation, namely the Implant Through Metal (ITM) scheme [2-6]. However, the implantation of dopant into the metal layer would possibly influence the thermal stability and the crystallinity of resultant thin silicide films on Si substrates. The Pd2Si silicide has the merits of chemical stability and oxidation endurance. Moreover, the Pd metal is also a heavy element and thus the knock-on of Pd atoms can be neglected during implantation through thin Pd films. Since the Pd2Si is a metal rich silicide, the reaction volume ratio of silicon to silicide is only 0.42 that is much smaller than 0.90 for TiSi2 and 1.04 for CoSi2 on Si substrates [7,8]. In addition, the Pd2Si formation temperature is relatively low, about 100 ~ 300 °C [7]. These peculiarities make Pd silicides be suitable for usage in low-temperature integrated-circuit processes. In this paper, the effects of phosphorus dopant on thermal stability and silicide crystallinity of thin Pd2Si or PtSi films on (100) Si substrates have been studied. Various thermal cycles and process
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